As disclosed in the above related application, a thin walled Dacron pouch or conduit is utilized to shunt blood from the left atrium of the heart to the descending throacic aorta in a left ventricular assist device. The device includes a rectangular cross section compression chamber for the Dacron pouch or shunt, the latter being equipped with a pair of Porcine valves near opposite ends of the compression chamber.
Within the compression chamber, a flat rectangular ejection plate is cyclically operated by the action of a connected follower element and a rotationally driven spirally grooved or slitted member connected with the output shaft of an electric motor driven by induction across the intact skin of a recipient of the device. The device of the prior application causes cyclic compression of the Dacron pouch to force predetermined volumes of blood from the left atrium into the descending thoracic aorta.
The present invention dispenses entirely with the rigid compression chamber, the ejection plate and associated mechanical drive means, thus eliminating, to a great extent, the hardware which must be implanted in the body of a recipient of a cardiac assist device of this type. Instead of these elements, the invention utilizes an artifical muscle in the form of a sheath surrounding the Dacron pouch or shunt, and cyclically this muscle sheath is electrically energized or stimulated to cause contraction of the muscle on the flexible shunt so that predetermined amounts of blood from the left atrium are pumped from the shunt into the descending thoracic aorta. The required stimulation and contraction of the artificial muscle sheath is obtained through the invention across the intact skin of the recipient by state of the art induction means which is operable to cyclically energize embedded electromagnets in multiple joined rod-like elastomer segments of the muscle sheath which also have magnetically attractable particles dispersed therethrough.
The construction of the assist device utilizing the artificial muscle in lieu of mechanical pumping means is much simpler and much more compact. The artificial muscle, being of a pliable nature, is more compatible with the portions of the human anatomy which are involved in comparison to the prior art.
While the electrically stimulated artifical muscle sheath is employed herein in a particular form of cardiac assist device, it should be understood that many other applications of the muscle can be visualized. The individual muscle segments can be joined together in sheets, rolls or other configurations and may consist of more than one layer of segments for various uses. Generally speaking, the narrower the individual rod-like segments are made and the more segments per artificial muscle layer, the greater is the degree of muscle contraction which can be obtained. The intensity of simulated muscle contraction is a function of current, the type and size of electromagnets employed, the type of elastic matrix, and the density of the ferromagnetic aggregate dispersed throughout the matrix.
Other features and advantages of the invention will become apparent during the course of the following description.